The present invention relates generally to improvements in grounding devices and it relates more particularly to an improved lay-in wire grounding lug for attachment to a conduit such as securement to the periphery of a bushing for mounting on a conduit.
Grounding lugs for conduit fittings such as is disclosed in the prior Browne U.S. Pat. No. 3,365,693, issued Jan. 23, 1968, are provided primarily for facilitating the grounding of conduit through a conduit bushing threaded onto the end of a conduit such as at a service box where the conduit passes through the wall of the box. This particular patent discloses the use of a grounding lug for laying in wire from the side so as not to require the wire to be cut and is generally adapted to be secured by a single screw to the periphery of a conduit bushing. The rear wall of the wire way and the top surface of the mounting tang are one and the same, so that the head of the securing screw oftentime is an obstruction in positioning the wire in the wire way. A clamping screw is provided for securing the wire within the lug.
Lugs of this type must be able to withstand heavy ground current flow which occasionally occurs under abnormal conditions such as because a phase to ground fault and the like, so that the lug must provide a low resistance connection from the conduit and service box to a substantially heavy ground wire. Oftentimes a single heavy ground wire is used for grounding a bank of conduits entering into a single box. Prior art devices of this type can accept a heavy ground wire, as long as the ground wire is perpendicular to the axis of the various conduits. However, if the ground wire is not perpendicular to the axis of the conduit, but generally parallel to the axis of any of the conduits, especially if the wire is used for a bank of conduits, the ground wire must be bent from the parallel position to the perpendicular position to be received with the lug. The heavy ground wire, usually made of solid copper conductor is difficult to bend, especially in cramped quarters, where many boxes or bushings on conduits are used, and difficult to avoid the obstruction of the mounting screw head. Also, since prior art grounding lug constructions of this type, in order to provide a low resistance connection from the lug to the conduit, provided the lug with teeth on the rear wall or base to prevent any rotation of the lug on the bushing, it was difficult, if not impossible, to rotate the lug in relation to the bushing to align the wire receiving portion with the wire. The prior art lugs possess numerous drawbacks and disadvantages, are often difficult to use in cramped quarters and otherwise leave much to be desired.